1. Field of the Invention
One aspect of the present invention relates to at least one of an aqueous ink composition and an image forming apparatus.
2. Description of the Related Art
Conventionally, an image forming apparatus such as an ink-jet printer that includes a head for ejecting a recording liquid such as an ink from plural nozzles and conducts ink-jet recording is known (for example, see Japanese Patent Application Publication No. 55-065269, Japanese Patent Application Publication No. 56-086789, Japanese Patent Application Publication No. 55-144172, Japanese Patent Application Publication No. 52-53012, Japanese Patent Application Publication No. 56-089594, Japanese Patent Application Publication No. 56-089595, Japanese Patent Application Publication No. 5-096720, Japanese Patent Application Publication No. 64-063185, Japanese Patent Application Publication No. 8-020159, Japanese Patent Application Publication No. 8-020161, Japanese Patent Application Publication No. 8-142500, Japanese Patent Application Publication No. 10-250216, Japanese Patent Application Publication No. 11-10856, Japanese Patent Application Publication No. 2000-044855, Japanese Patent Application Publication No. 2000-063719, U.S. Pat. No. 4,538,156, U.S. Pat. No. 5,099,256, Japanese Patent Application Publication No. 62-092849, Japanese Patent Application Publication No. 11-188858, Japanese Patent Application Publication No. 2000-343808, Japanese Patent No. 3658765, Japanese Patent Application Publication No. 2003-246135, Japanese Patent Application Publication No. 2002-370441, Japanese Patent Application Publication No. 2005-170036, Japanese Patent Application Publication No. 2003-82265, Japanese Patent Application Publication No. 2008-019286, Japanese Patent Application Publication No. 2010-188665, Japanese Patent Application Publication No. 2007-023297, Japanese Patent Application Publication No. 2005-344100, Japanese Patent Application Publication No. 2004-018640, Japanese Patent No. 3595805, Japanese Patent Application Publication No. 2003-089752, and Japanese Patent Application Publication No. 2004-026947).
In ink-jet recording, ink is ejected from a miniature nozzle of several dozen and hence, a dye with a high solubility has been used as a coloring agent for an ink in view of a problem of ink clogging, etc. A dye ink is excellent in its coloring property, and as a result, it is possible to obtain an image quality in a photographic print which is comparable to that of a silver halide photograph, but has a problem of degradation in an image preserving property such as a water-resistant property, a light-resistant property, or a gas-resistant property. In order to compensate for such a problem, utilization of a pigment as a coloring agent for an ink has been advancing and its installation is also made for a printer in a personal market or office market as well as an industrial wide-format printer.
For printing a color image or character on a plain paper sheet, permeability of an ink into a paper sheet has been improved by adding a surfactant, etc., to an ink to suppress its bleeding (spreading) at a color border of an overlap portion of two colors, etc. (for adding a surfactant, etc., into an ink, see, for example, Japanese Patent Application Publication No. 55-065269). Although it may be possible to reduce bleeding at a color border by improving permeability of an ink into a paper sheet, its permeation occurs along a cellulose fiber forming a plain paper sheet and hence bleeding (feathering) may readily occur at a peripheral portion of a printed image such as a character or fine line.
An idea of using an ink with a low permeability only for printing a black character, etc., has been applied to attain prevention of both bleeding and feathering, but in that case, there may remain a problem that dryness of a black ink may be low and high-speed character printing may be difficult.
Then, an ink-jet-dedicated recording medium that is preliminarily coated with a material (a water-soluble polymer, a white pigment, etc.) for fixing a coloring agent in an ink has been proposed (for example, see Japanese Patent Application Publication No. 56-086789, Japanese Patent Application Publication No. 55-144172, Japanese Patent Application Publication No. 52-53012, and Japanese Patent Application Publication No. 56-089594). Such a dedicated paper sheet suitable for ink-jet recording is used so that an image quality may be improved significantly. However, there may be a problem in the cost of a dedicated paper sheet, and hence, printing of a character on a plain paper sheet at a high image quality is desired, in particular, in a business application.
For application to a general recording medium such as a plain paper sheet, an ink-jet recording method has been proposed wherein a solution of a polymer such as carboxymethyl cellulose, polyvinyl alcohol, or polyvinyl acetate is preliminarily jetted onto a recording medium and then character printing is conducted by ejecting an ink onto a portion to which such a polymer solution adheres (for example, see Japanese Patent Application Publication No. 56-089595). However, such a polymer solution may not suppress feathering and a water-resistant property may also not be improved.
Furthermore, an apparatus for forming an image by using an ink-jet recording head has been proposed wherein such an image forming apparatus has means for applying a water-absorptive resin particle(s) for absorbing an ink on a recording medium, means for ejecting an ink onto the water-absorptive resin particle(s) applied on the recording medium, and means for fixing the water-absorptive resin particle(s) on the recording medium (for example, see Japanese Patent Application Publication No. 5-096720). However, a water-absorptive resin particle(s) may readily absorb moisture or be aggregated due to water absorption in an apparatus or at the time of storage whereby some deficiencies may readily occur, for example, it may be difficult to apply a water-absorptive resin particle(s) on a recording medium uniformly.
Furthermore, an ink-jet recording method has been proposed wherein a pretreatment fluid for recording medium which includes a compound for insolubilizing a coloring agent in an ink is adhered to a recording medium by an ink-jet method and subsequently an ink is ejected onto a portion to which such a pretreatment fluid for recording medium adheres, so that an image is formed (for example, see Japanese Patent Application Publication No. 64-063185, Japanese Patent Application Publication No. 8-020159, and Japanese Patent Application Publication No. 8-020161). In such a method, improvement at some level on both bleeding and feathering may be attained. However, in such a method, it may be necessary to reduce a viscosity of a pretreatment fluid in order to eject the pretreatment fluid stably, and hence, a compound for insolubilizing a coloring agent may necessarily be provided at a low concentration. It may be necessary to provide a comparatively large amount of a pretreatment fluid in order to obtain a sufficient effect of improving an image quality by means of such a pretreatment fluid and a large amount of a liquid including water is provided on a recording medium, whereby curling or cockling of a recording medium may readily occur.
Furthermore, an image forming method has been proposed wherein a colorless liquid composition that contains at least a silicone compound such as a silicone oil and a cationic compound is applied on a recording medium and subsequently an ink that contains an anionic component is adhered to the recording medium by an ink-jet recording mode (for example, see Japanese Patent Application Publication No. 8-142500). However, there may be a problem that a permeability of an ink into a recording medium portion to which a silicone compound adheres may be significantly low and hence drying of an image portion may be slow.
Furthermore, in order to improve a permeability or wettability of an ink, a method for forming an image has been proposed wherein an image recording promotion fluid that contains a compound for insolubilizing a coloring agent and a predetermined surfactant is provided on a recording medium and subsequently an ink is adhered to the recording medium by an ink-jet recording mode (for example, see Japanese Patent Application Publication No. 10-250216). According to such a method, a surfactant in an image recording promotion fluid may improve a permeability or wettability of an ink for a recording medium so that drying of an image may be improved to allow application of high-speed recording, but a quantity of a component for insolubilizing a coloring material may be small so that an effect of preventing bleeding or feathering may be insufficient, whereby a further improvement is desired.
Furthermore, a technique has been proposed in which a reaction fluid that contains a multivalent metal salt for insolubilizing a coloring agent in an ink is applied on a recording medium (for a reaction fluid containing a multivalent metal salt, for example, see Japanese Patent Application Publication No. 11-10856, Japanese Patent Application Publication No. 2000-044855, and Japanese Patent Application Publication No. 2000-063719). An image quality may significantly be improved by such a technique.
Meanwhile, a method called an intermediate transfer mode has been proposed wherein an ink image is formed on an ink-impermeable intermediate transfer body by an ink-jet recording method and subsequently the ink image is transferred from the intermediate transfer body to a recording medium (for example, see U.S. Pat. No. 4,538,156 and U.S. Pat. No. 5,099,256). In an intermediate transfer mode, it may be possible to arrange a recording head away from a recording paper sheet and it may be possible to suppress clogging caused by adhesion of paper powder on a nozzle of a recording head. Furthermore, although it may be generally difficult to keep always a gap between a recording head and a recording paper sheet constant, it may be possible to keep a gap between a recording head and an intermediate transfer body constant and provide a good compatibility with a kind of paper, so that a mode using an intermediate transfer body may have a high reliability. However, when an intermediate transfer body is made of a material with a good release characteristic in order to obtain a high transfer rate, there may be a problem that an aggregate of adjacent fluid drops, called a bleeding or beading, may readily and severely be produced and an image quality may readily be degraded.
For improving such an intermediate transfer mode, a method has been proposed in which an ink is ejected onto an intermediate transfer body to form an ink image and subsequently most of water in the ink is vaporized on the intermediate transfer body to transfer a concentrated ink onto a recording medium such as a paper sheet (for example, see Japanese Patent Application Publication No. 62-092849). In such a method, once a good image is formed on an intermediate transfer body, it may be possible to obtain an image with a good quality, even on a so-called plain paper sheet that is commonly used. However, time may be consumed for concentrating an ink at an ordinary temperature, and hence, it may be necessary to heat an intermediate transfer body so as to promote vaporization of a solvent in an ink, and as a result, there may be a problem that a large amount of energy may be needed.
Furthermore, a method has been proposed in which a particle of a water-absorptive resin such as polyacrylic acid is provided on a surface of an intermediate transfer body to absorb water in an ink provided on the intermediate transfer body and subsequently transfer onto a recording medium is conducted together with the particle of a water-absorptive resin (for example, see Japanese Patent Application Publication No. 11-188858 and Japanese Patent Application Publication No. 2000-343808). Although it may be possible for such a method to obtain an image with a good quality even on a plain paper sheet, there may be a problem that an aggregate of water-absorptive resin particles may be provided by means of moisture absorption at time of storage and it may be difficult to conduct uniform application on an intermediate transfer body, etc., similarly to a technique using means for applying water-absorptive resin particles for absorbing the above-mentioned ink on a recording medium, etc.
Furthermore, a method has been proposed in which a reaction fluid that contains a multivalent metal salt or polyallylamine reacting with a component of an ink is adhered to an intermediate transfer body and provided onto a recording medium before or after an ink is ejected onto the recording medium to form an image (for example, see Japanese Patent No. 3658765). It may be possible for such a method to reduce a reaction fluid adhered to a recording medium compared to a conventional method and reduce curling or cockling caused on a recording medium.
Furthermore, an image forming method has been proposed wherein a treatment fluid that contains a cationic polymer compound and a surfactant and/or a wetting promoting agent is provided onto an intermediate transfer body to contact and mix the treatment fluid with an ink ejected by an ink-jet mode and subsequently transfer to a recording medium is conducted (for example, see Japanese Patent Application Publication No. 2003-246135).
Similarly, an image forming method has been proposed wherein a treatment fluid that contains a multivalent metal salt which reacts with an anionic ink coloring agent to cause aggregation, etc., is provided onto an intermediate transfer body to contact and mix the treatment fluid with an ink ejected by an ink-jet mode and subsequently transfer to a recording medium is conducted (for example, see Japanese Patent Application Publication No. 2002-370441, Japanese Patent Application Publication No. 2005-170036, and Japanese Patent Application Publication No. 2003-82265). More specifically, it has been proposed that a water-soluble resin with a minimum filming temperature (MFT) less than or equal to 30 degrees is further contained in an ink or a treatment fluid whereby it may be possible to further provide a rub resistance to an image (for example, see Japanese Patent Application Publication No. 2002-370441). It has also been proposed that it may be possible to provide a water-soluble resin onto an image before transfer to provide a rub resistance similarly (for example, see Japanese Patent Application Publication No. 2005-170036). It has been proposed that a resin emulsion having an ionic group on a resin particle surface, as one more reaction component other than a coloring agent that reacts with a treatment fluid, is further contained in an ink to enhance an aggregating power of a coloring agent due to an additional effect of causing aggregation (for example, see Japanese Patent Application Publication No. 2003-82265).
It has also been proposed that when contact and mixing with an ink is conducted, a treatment fluid for significantly changing a pH of a mixed fluid is provided onto an intermediate transfer body (for example, see Japanese Patent Application Publication No. 2008-019286).
Such a reaction fluid or treatment fluid may be effective to solve a problem (bleeding, feathering, or beading) associated with a quality of an image on an intermediate transfer body or a recording medium. However, when a reaction fluid or treatment fluid is applied an entire surface of a paper sheet or intermediate transfer body, there may be a problem of inefficiency because of an unused non-image portion. Furthermore, a consumable supply other than an ink may increase, and hence, there may be a problem that a running cost may increase. Furthermore, a reaction fluid or treatment fluid is based on water, so that an amount of water absorbed in a paper sheet may increase ultimately and curling or cockling may readily occur. When a printing rate increases, such curling or cockling tends to be significant, which may be problematic. Hence, where possible, it may be desirable not to use such a reaction fluid or treatment fluid.
Besides spreading or color mixing on a recording medium such as feathering or bleeding, there may be a problem in a fixation property (rub resistance) in a case of a pigment-type ink coloring agent. As a method for improving a fixation property, it has been proposed that a resin emulsion is contained in an ink (for example, see Japanese Patent Application Publication No. 2004-026947). Furthermore, a resin may be needed for improving a fixation property of a pigment particle on a surface of a recording medium, as it has been proposed that a comparatively low-molecular water-soluble resin instead of a resin emulsion is contained in an ink.
As described above, various propositions have been provided in order to conduct recording on a plain paper sheet with a high image quality, a high speed, and a high reliability.
In a circumstance as described above, it is desired that an ink composition capable of obtaining an image with a high image quality and less feathering, bleeding, or paper sheet curling on a plain paper sheet and an image forming apparatus using the same are proposed. Furthermore, it is desired that an ink composition capable of obtaining an image with a high image quality, a good fixation property, and a high image density on a variety of recording media using a consumable supply other than an ink such as a reaction fluid or treatment fluid as little as possible and an image forming apparatus using the same are proposed. Furthermore, it is desired that an energy-saving ink composition which may not need a large amount of thermal energy to vaporize water in an ink on an intermediate transfer body and an image forming apparatus using the same are proposed.